Coded track circuit



July 18, 1944.

A. L. JEROME CODED TRACK IRCT Filed Oct. 29. 1943 6 Sheets-Sheet l y www INVENTQR LIL A. JEROME c onsvrmck CIRCUIT f July 18, 1944.

6 Sheets-Sheet 2 Filed Oct. 29, 1943 INVENTOR aPL.Je10me.

HIS ATTORNEY July 18, 1944.

A. L. JEROME CODED TRACK CIRCUIT Filed Oct. 29, 19435 G Sheets-Sheet 5 IZIS ATTORNEY July 18, 1944.

A. L. JEROME GODE!) TRACK CIRCUIT Filed Oct. 29, 1945 6 Sheets-Sheetl 4 HAL *G01/ennui by C INVENTOR APhaPL .Jerome E" L11/XM HIS ATTORNEY July 18, 1944- v A. 1 JEROME 2,354,024

CODED TRACK CIRCUIT HIS AvroRNraYv July 18, 1944. I A. L. JEROME coman Tmcx crncum 6 Sheets-Shoe*l 6 Filed Oct. 29, 1943 Patented July 18, 1944 2,354,024 v CODED TRACK CIRCUIT Arthur L. Jerome, Edgewood, Pa., assignor to The Union Switch & Si

gnal Company, Swissvale,

Pa., a corporation of Pennsylvania Application October 29, 1943, Serial No. 508,192 1s claims. (o1. 24e-ss) My invention relates to railway signaling systems of the coded track circuit type which employ the coded feed-back operating principle shown in` Letters Patent of the United States N o. 2,021,944 to Frank H. Nicholson.

An object of this'invention is to provide improved coded track circuits of the type described in which successive impulses of feed-back code are of opposite relative polarity. Y

A further object of' the invention is to provide improved ,coded feed-back trackcircuits of the type described in which the feed-back detector relay is of the polarized type and is operated solely by energy supplied from the entrance end of the section to thereby provide a maximum of protection against false operation of the detector relay by foreign current.

Another object of the invention is to provide improved coded track circuits of the type described and incorporating means for discontinuing operation of highway crossing signals when a train vacates the approach section leading to a highway intersection.

A further object of `the invention is to provide improved coded track circuits of` the type described which are arranged so as to'premit imq pulses of coded alternating current energy of standard pattern to -be supplied to the rails of a track section to operate existing cab signal equipment on locomotives operated throughthe track stretch. o

Another object of this invention is to provide improved coded track circuits of the type described in which the impulses of master code are supplied to the track rails in series With the Winding of the detector relay to thereby prevent operation of the detector relay by energy stored in the track circuit.

A further object of this invention is to provide improved coded track circuits of the type described in which the impulses of feed-back code are supplied to the track rails in series with the winding of the track relay to thereby kprevent operation of the track relay by energy stored in the track circuit.

A further object of the invention is to provide improved coded track circuits of the type described and incorporating means for supplying feed-back energy to the rails of an occupied'section to detect when the section is vacated.

Another object of this invention is to provide improved coded track circuits of the typev described and incorporating means for selectively controlling the polarity relationship of successive impulses of feed-back and master code supplied to the rails of a track sectiony and for distinguishing betweenthe -tWo types of feedback energy at the exit end of the section.v

A further objectof the invention isrto provide improved coded track circuits which are 'arranged Asofthat the master code impulses supplied to therails of a section are relatively short as long as the section is vacant, and so that when the section isfoccupied the length ofthe master code impulsesisrincreased vvto make these Yimpulses substantially as long as the intervals between impulses.

I shall describe several 'forms' of coded'track circuit `apparatus embodying my invention and shall then point out the novel features thereof in claims. e f

In the drawings, Fig. 1 is a diagram of asection of railroad track equipped with track circuit apparatus embodying my invention, and .Y

Figs. 2 to K11, inclusiveyare'diagrams showing modifications which I may employ. i

Similar reference characters lreferfjo similar parts in each ofthe several view In practicing my inventionIemploy a track relay and a .feed-back detector relay'of the stick polar type, while ISupply' to thesection rails impulses of master code which are relativelyshort and alternate impulses of which are of opposite relative polarity. During the periods between successive impulses of master code I supply to the section rails impulsesof feed-back code which are relatively jshort and alternate impulses 'of which `are of opposite relative polarity.` `The supply of master code and feed-backV energy to the lsection railsis controlled yby impuls'rerelays the contacts of which Vwhenreleased connectr the track or feed-back detector relay across the section rails' and which when picked up connect the track or feed-back battery across the section rails, While means governedby a contact of a code transmitter' or by a contact of the track VrelayV is providedfor supplying' to the impulser'elays, irnpulses of energy elect'iveto maintain their contacts picked'up for a predetermined period only. The polarity of the impulses of master code may be governed by a contactbf the feed-back Vrelay or by a contact of ,the coding device, while the polarity of the impulses o'flfeed-back energy may becontrolled by a contact of the track relay or lby a Contact of areny controued by the track'relay.'

Where cab signalsr are employedmeans is prolvided to operate the impulse relay at the'exit end of an occupied` section as a repeater of the code `transmitter to thereby causeV alternating current impulses of standard code pattern to be to the section rails so that locomotives cab signal apparatus may with this track section are separated from the rails of ad-v joining sections by insulated joints 3 in the usual manner. A Wayside signal S is trance end of the section and as shown is of the familiar color light type and has Va green or clear lamp G, a yellow or caution lamp Y, and a red or stop lamp R.

The track section is equipped with track circuit apparatus embodying this invention. The equip.

ment at the exit end of the section includes a coding relay CTM which is operated atone or another of a plurality of different rates determined by traffic conditions in advance, While the energy for operating relay CTM may be; controlled by contacts of continuously operating coding devices I5CT and ISUCT. The relay controls the supply of energy to relays MRr and MRP, which control the supply of energy from the-track bate tery TB to the section rails and alsoA control connection of thepolarized feed-back detectorrelay K across the section rails, whllethe relay CITM also controls the polarity of the energy supplied from the track battery to the section rails.

rI he equipment at the entrance end of the track section includes a polarized track` relay TR, a decoding transformer DT, decoding relaysH and J, a pole changing relay PC which governs the polarity of the energy supplied from the `feedback battery FB tothe section rails,` and impulse relays IR and IRP which control connection of the feed-backbattery acrossthe section rails and also control connecticnlof the" track relay across thesectionrails; s.

The equipment at each end'ofthe track section includes a source ofdirect current, such as a storage battery, not'shown, the terminals of which are designatedrB andC in'thedrawings.

The equipment is shown in the condition which itassumes when the track stretch is vacant.' At this time relay HA, which is governedby traino in the section in advance of that shown, is picked up and its'contact I0' establishe's'the circuit including a contact of code transmitter I80CT for supplying energy to coding'relay so the contacts of relay CTM are pickedup and released 180 times aminute.'Y 1 j Each time the contactsof relay CTM pick up or release the contact IIY causes a change in energization of the primary winding'of transformer MT, and an impulse oi energy is supplied from the transformer secondary windingU through a rectier to relay MR,'and also over back contact I2 f relay MR to relay MRP. Accordingly the contacts of relays MRl and' MRP pick up, and'con'- tact I2 of relay MR establishes a stick circuit for relay MRP. f f

When relays MRand MRPLpi'ck up the circuit of relay K is interrupted while the center or neutral terminal of the track battery TB is connected to track rail 2 over front contact I4 of relay MRP and front contact I5 of relayMR; When relay CTM is picked up its contact/I6 connects track rail I with the upper or positive terminal of the track battery so that energyv of normal polarity is supplied to the section rails, while when relay CTM is released contact I6 connectsA track rail located at the en-A l rupts the stick circuit with the lower or negative terminal of the track battery so that energy of reverse polarity is supplied to the section rails.

The transformer MT and the relay MR are proportioned so that the impulse of energy supplied to relay MR from the transformer on each movement of the contacts of relay CTM will cause the contacts of relay MR to. pick up and remain picked up for a predetermined relatively short interval. Relay MRP also picks up when relay MR picks up, while relay MR when picked up establishes a stick circuit for relay MRP so that relay MRP remains picked up as long as relay MR is picked up. On release of relay MR its contact I2 interfor relay MRP so relay MRP releases. However, the relay MRP is of a type the contacts of which are slightly slow in releasing so its contacts remain picked up for a short period after release of relay MR.

On release of relay MR its contact I5 interrupts the circuit of the track battery and cuts oir the supply of energy to the trackrails, but relay K is not connected across the Section rails until relay MRP releases. The release period of relay MRP is long enough to permit energy stored in the track circuit to be dissipated so that when relay MRP releases and its contact I3 completes the circuit for connecting relay K across' the track rails, there is no danger that the relay K will' be operated by energy stored inthe track circuit.

It will be seen, therefore, that .ea-chtime the contacts of relay CTM pick up or release the relays MR and MRP pick up for a short periodfto cause an impulse of master code' to be supplied from the track battery to the section rails, while the relays MR and MRP thereafter release and connect the relay K across the section rails. In addition, it will be seen that the impulses oi master code supplied to the section rails are of normal polarity when relay CTM is picked up and are of reverse polarity when relay CTM is released so that successive impulses of masterA code are of opposite polarity.

The impulses of master code suppliedto the track rails feed to the track relay TR over the circuit which is traced from rail I through the winding of relay TR, back contact 20 of relay IRP and back contact 2l of relay IR to rail 2.l The impulses of `master code of normal polarity supplied to relay TR cause the contacts of this relay to move to their left-hand or normal positions, while the impulses of reverse polarity supplied to relay TR move the' relay contacts to'their lright-hand or reverse positions. l

On each movement of the contact 22 of relay TR'there is a change in energization of the primary winding of transformer DT with the result that an impulse of energy is induced in each of the secondary windings of this transformer. Energy from one of these windings is rectified by contact 24 of relay rTR and is supplied to the winding of relay H so that contact 25 of relay H is picked `up when and only when relay TR is following code. P

Energy from another winding of transformer DT is supplied to relay J through a resonant rectier unit IBIJDU, the elements of which are proportioned to supply sufficient energy to relay J to pick up its contacts only when relay TR is responding to energy of 18(1)'code frequency. At this time relay TR is supplied with energy of code frequency so relay J` is picked up and energy is supplied to the green lamp G of signal S over the circuit which'in'cludes front contact 25 of relay H and front contact 26 of relay J.

Energy froml another secondary Winding of transformer DT isisupplied through an impulse transformen IT to relays I R and IRP which operate inthe same manner as relays MRand MRP. When relay IR picks up, its contact 28 `establishes a stick; circuit for relay IRP, While when relaysIR and IRP are picked up, the cir-A cuit of relay TR is interrupted and the neutral orcenter terminalof the feed-back battery FB is connected over front contactll of relay IRP and -front contact 2l of relay IR to track rail 2. When Contact .ZZ of track relay TR is in its reverse position, venergy is vsupplied through an asymmetric unit 3| to/.pole changing relay PC and its contactSZ connects track rail l to the upper or negative terminal of the feed-'back `battery FB, while when the Contact 22 of relay TR is in its normal position, energy is fnot supplied to relay P C and its contact 32 is released sorthat rail vl is connected to the lower or positive terminal of the ybattery FB. Y i

' On each movement of the contactsvof the track relay TR energy is supplie-d tothe relays IR and IRP and theircontacts pickup momentarily and connect the battery FB across the section. rails. After a brief .timeintervalrelay IR releases and interrupts'the stick circuit for relay IRP so that it releases and connects the track relay TR across the section rails., On movement of the track relay contactsto their normal positions relay PC is released so theimpul'se of feed-back energy supplied to the section rai-ls is of normal polarity, ,While on movement of the track relay contacts to their reverse'positionrelay PC is picked up so the'i-mpulse ofvfeed-back energy supplied to the section rails is of reverse polarity.

From the foregoing itA will be seen that each time the' contacts of relay CTM pick up, the relays MR and MRP'pick up momentarily4 and cause an impulse of master'code of normal polarity to be'ts'uppliedto the "track rails. f This energy feeds 'over back contacts 20 and 2l of relays IRP and IR to relay. TR and moves its contacts to their normal positions. On this movement of the contacts 'of relay TR relay APC'releases.While relays IR and IRPv pick up so an impulse of feed-back energy of normal polarityvis supplied to the section rails.

When relays IRv and IRP pick up the circuit of trackrelay'TR'is interrupted, but as picking up of relaysV IR and IRP is dependent on movement 'ofthe' contacts of track relay TR, the contacts of `relayv TRYWill4 have completed their movement before relaysIR and LIRP pick up so interruption Aofthe circuit of relay TR is without consequence. Furtlierrnorejthe relay TR is of a type the contacts of whichV when `moved to either position remain in that position until energy of the polarity effective to move the relay contacts `to their other position i's'supplied to the relay. Accordingly,- the circuit of therelay TR may be interrupted as soon as its contacts ymove from one position to the other. ,f

. The impulse of feed-back energy of normal polarity supplied to thesection rails is supplied 'over back contaets I5 and lI3 of .relaysMR and `MRP to relay Kane itseontacts move to their normal positionslas shown. Y

. The Various parts'of thetapparatus are propertioned so'that on picking up of relay CTM the relays MR and MRP will pickup and remain picked lup long enough to insure that the impulse of mas- `tercode'supplied tothe trackrails Will operate the track relay TR. t. .The relays MR and MRP fr eleaseand connect the relayK across the section .railssub'stantiallylas soon as the relayS I-Rand 7 5 IRP pick up to supply-an impulse of feed-back en'fl ergy to the section rails. Furthermore, there is a relatively long period from lreleasepof relays MR and MRP until they pick up again so thecircuit of relay yK is established long enoughto in-v sure that the relaywill respond tothe impulse of feed-back energy supplied overthe section rails. f Similarly, when relay CTM releases thereiays MR and MRP pick up and cause an impulse of master code of reverse polarity: to be supplied to the section rails. When relays MR and MSRP pick up thecircuit of relay K is interrupted, but before this occurs the relay K will have respond, ed to the impulse of feed-back energy supplied to the track rails. Likewise, at or before the time that the relays MR andMRP pick up, relays IR and IRP will release and establish thecircuit of relay TR so that the impulse of masterv code of reverse polarity feeds to this relay and moves its contacts to their reverse .positionsA so that relays PC, IR and IRP pick up to cause an impulse offeed-back energy of reverse polarity to be supplied togthe section rails. This impulse ofl feed-back energy will move the contacts oi. relayv K to their reverse positions. v

The operation of .the equipment is such, t therefore, that each time the contacts of relay CTM pick up, an impulse of master Code ofrnormal polarity is supplied to the section rails, and each time the contacts of vrelay CTM release, an im; pulse of master code of reversepOlarityris supplied to theV section rails. As long as the section is vacant these impulses of master code feed to the track relay and operate it 4so that relays H and J arepicked up, while eachtime the con'-` tacts of the track relay move, the relays IR and IRP pick up and cause an impulse of feed-back energy to be Asupplied to thesection rails.. The impulses of feed-back energy occurin the inf tervals between thel impulses of master code. While successive impulses of feed-back energy are o f oppositepolarity so that the contacts ofrelay K are operated iirst to one: position vand thento the. other. l f 1 .A slongas the sectionis vacant, the contacts;

o f relayK are operated between'their two positions and energy is suppliedthrough the trans-,- former KT tothe relay nK'Hand the contact 3 4 of relay KI-I vis pickedup, The circuit or circuits governed by contacted lof-;relay,KH may be Aem-A ployed for any appropriate purpose as, for example, to control lightingof the signal lamps of the signal for the adjacent section vin advance or to c ontrol locking of a switch, not shown, When-a 4train enters the track section, the trackV relay TR is shunted and ceases to follow code;

while energy is no longer supplied through the decodinghtransformer DT ,to therelays. Hand J and they release so that the green lamp G'is extinguished and energy is supplied to the red lampR of vsignal S over back contact 25 of relay H. addition, energy, is no longer supplied to;

relays IR and IRPand they remain released'and do not supply energy; from the feed-back battery to the section rails. As the supply of feedfback energyto the Vsection rails is ,cut off, relay K1 ceases-to operate and relay KH releases. a At this time, relayCTM continues to operate so impulses of master code are supplied to thel track rails, and when the section is vacated,.these Vfeed to the track relay and operate it so that relays IRand IRP again cause feed-back energy to be supplied to thesection rails, While yrelay H' is pickedup .and relay J may` alsobe picked. 1110.-'.

The feed-back energy supplied to the section r-ails feeds to the relay K and operates it so that energy is supplied through transformer KT to relay KH.

In this system the feed-back detector relay K is operated solely by energy supplied from the entrance end'of the track section, while in order to operate the relay K, successive impulses of feed-back energy must be of opposite polarity. This substantially eliminates the possibility of operation of relay K by foreign current when the track section is occupied. A

When the'section is occupied, the track relay is shunted and does not cause relays IR and IRP to supply impulses of feed-back energy to the track rails. At this time relay CTM continues to operate so relays MR and MRP pick up to cause impulses of master code to be supplied to the section rails and at the same time to interrupt the circuit of relay K, while the relays MR and MRP subsequently release and connect the relay K across the section rails. 'Ihe relay K is of the stick polar type and when the circuit of the relay Winding is interrupted, the relay contacts remain in the position which they then occupy.

Foreign current when present is of one relative polarity. Accordingly, when relays MR and MRP releaseiat a time when the section is occupied and foreign current of a value high enough to operate relay K is present, the foreign current will hold the contacts of relay'K in the position which they then occupy if the position ofthe contacts of relay K and the polarity of the foreign current are in correspondence. If the position of the contacts of relay K and the polarity of the foreign current are out of correspondence, the energy supplied to relay K the first time the winding of relay K is connected' across the section rails will move the contacts of Arelay K into correspondence with the'polarity of the foreign current, while the relay contacts are heldin this position -by the energy supplied to relay K during subsequent periods in which the relay Winding is connected across the section rails. Y

Energy is supplied through the transformer KT to the relay KH only when the contacts of relay K are continuously moved between their two positions, and as foreign current supplied to relay K serves to holdV the relay contacts in one position Athere is no'possibility that the supply of foreign current to the relay K will result in energization of relay KH. 'Y

The track circuit provided by this invention may be modied-to provide for the supply of coded alternating current cab signal control energy to the rails Yof an occupied section and Fig. 2v shows such a modification.

Construction and operation ofV modification shown v inFinz The modification shown in Fig. 2 is similar to that shown in Fig. l, but differs 'therefrom in that a track transformer TT has its secondary winding connected in series with the track `battery TB, while the equipment at theeXitend of the section is arranged so that when the section is occupied the relays MR 'and MRP 'operate as repeaters of the` coding relay CTM instead of as impulse relays. y v

The equipment at the entrance end of the section Yshown in Fig. 2 differs Vfrom that rshown in Fig. l in that means is provided vfor supplying feed-back energy to an occupied sectionv to reset the track circuit when the section is vacated.

A wayside signal is not shown in Fig. 2 but such a signal may be provided if it is desired.

The modification shown in Fig. 2 is intended for use in track stretches through which are operated locomotives equipped with cab signal apparatus responsive to ow of coded alternating current in the track rails. The locomotive cab signal equipment may be constructed as shown in Letters Patent of the United States No. 1,986,679 to Lloyd V. Lewis.

The apparatus of Fig. 2 is shown in the condition which it assumes when the track stretch is vacant. At this time relay KH is picked up and its contact 34 establishes the circuit of' contact Il of coding relay CTM so that energy is supplied through the transformer MT to relays MR and MRP and they operate as explained in connection with Fig. 1 to supply impulses of master code of lalternate polarity to the* section rails, and to connect the relay K across the section rails in the periods between the impulses of master code to the track rails.

In addition, as relay KH is picked up, its contact 35 short-circuits the primary winding of the track transformer TT.

The master code supplied to the section rails operates the track relay TR so that energy is supplied through the decoding transformer DT to the relay H, and it is picked up so that its contacts 36 and 31 connect the primary winding of impulse transformer IT to a secondary winding of transformer DT so that, on each movement of the contacts of the trackrelay, an impulse of energy is supplied through the impulse transformer to the relays IR and IRPand they operate in the mannerv explained in connection with Fig. i to supply impulses of feed-back energy to the section rails. In addition, contact 38 of relay H connects relay PC to a stationary contact associated with track relay contact 22 so that relay PC causes successive impulses of .feed-back energy to be of opposite polarity.

When a train moving in the normal direction of trac enters the track section, the relay K is shunted and ceases to follow code so energy is no longer supplied through the transformer KT to relay KH and the contactsof vrelay KH release so that contact 34 interrupts the circuit of contact H of coding relay CTM and establishes the circuit of coding relay contact 40. Accordingly, energy is no longer supplied through the transformer rMT to the relays MR and MRP, but each time the contacts of relay CTM pick up, energy is supplied over its front contact 40 to the relays MR and MRP so that they pickn up and remain picked up throughout the entire picked-upperiod of the contacts of relay CTM. In addition', when relay KH releases, its contact 35 establishes the circuit to supply energy to the primary winding of track transformer TT from a source of alternating current energy, the terminals of which are designated BX and CX.

Accordingly, each time the contacts of relay CTM pick up, the contacts ofl relays MR and MRP pick up so that the track transformer TT is connected across the section rails and alternating current is supplied to the section rails. At this time the relays MR and MRP are direct repeaters of the relay CTM so the alternating current supplied to the track rails is coded in the normal manner and will operate cab signal equipment of standard construction.

When the section is occupied, the track relay is shunted and energy is no longer supplied through the transformer DT to lrelay H so relay H releases vand its contacts 36 and 31 transfer connection of the p'rin'iary winding of transformer IT from a secondary Winding of decoding transformerl DT to contacts of a coding device 20CT, while contact 38 of relay H transfers control of relay PC from track relay contact 22 to a contact of coding device ZDCT. The contact ofthe coding device 20CT is continuously operated between its two positions so vthat when relay His released, the two portions of the primary winding of transformer IT are alternately energized, while each time the contact of the device 2IJCT moves to its lower position, energy is supplied to therelay PC. Accordingly, on movement of the contact of the device ZUCT to either of its two positions, an impulse of energy is supplied through the trans'- former IT to the relays IR and IRP so that they pick up momentarily andnestablish the circuit-'of the battery FB and thus cause impulses of feedbacky energy to be supplied to the section rails, while relay PC causes alternate impulses of feedback energy to be ofv opposite relative polarity. As long as the section isjoccupied', the relay K is shunted and theimpulsesof feed-back energy supplied do not operate Lthe relay K.

When the train vacates the section, the impulses of feed-back energy fee'd to the relay K and operate it tocause energy to be'supplied through the transformer KT to the relay KH,

At the time the section is vacated, the relays MR and MRP are` being picked' up and released at the rate determined by therate of operation of relay CTM. The rate of operation of the coding" Y device 2BCT is substantially different from that of the coding devices IECT and I88C'I with the result that there are frequently recurring periods in which the relaysIRfandv IRP are picked 11pto cause impulses of feedfbackenergy to be supplied to the track rails,.and the relays MR yand MRP are released to permit energy from thetrack jrails to feed to the relay K. Accordingly, the feed-back energy Vwill operate` the relayfK soI that relay.v KH ispickedup.l l

When. the contactsof relay,- KH pick up, contact cuts oli" the .supply of energy to the track transformer TT andshort-circuits thetrack transformer primary winding, while contact 34 inter' rupts the circuitl of contact dil of coding yrelay CTM and establishes the circuitof contact H of relay CTM. Accordingly, relays MRand MRP cease to operate as repeaters of relay CTM, while impulses ofenergy are supplied 'through' trans-V former MT to relays MR and MRP "sor that they operate in the usual manner tosupply impulses of master code of alternate relative polarity tothe section rails. f

Because ofthe differencein the rate of opera-- tion of the relays. M R and MRP and of the relays IR and IRP, there are frequently recurring. periodsduring whichk the track relay 'IR is con-` nected across the sectionv rails at a time when impulses cf master codeare supplied to the section rails.l The impulses of master code. therefore, will feed to the track relay and operate it so that energy is supplied through the decoding transformer DT to relay I-l, and its contacts pick up so that the primary winding of transformer IT is transferred from codingy device 26CT to a secondary winding of transformer DT, whileV control of relay PC is transferred from coding' device EGCTto contact Ziof the track relay TR. The equipment at the entrance end of the section now operatesn the normal manner to supply an impulse of feed-back energy to the section rails following each movement 'of the track relay concoding device 20er, and Fig. 3 is tacts, while the r'e'lay vPC causes alternate impulsesf of 'feed-'back' energy-to be of opposite po- 1aray.=- v

v From the" foregoing it wiiibe soon that, when th'e section is vacant, an impulse of master code "is supplied to the section rails each time the contacts of relay CTM lpckup or release, while the 'impulses of master'code-fare much shorter than the picked-upland released periods of the contacts of relayCTM. "In addition, when Athe section i's-vacant,thelsupply'of feed-back energy is gov# ve'rned by response of thetrack relay toimpulses of master code. When"'thejsection 'is' occupied, control ofrelays MR and MRP is transferred to a contact of relay-CIM so that these relays op' erate as repeatersof th'e relay CTM-and supply tothe trackfrails codedl energy in'which the energy impulses are substantially as'long as thein-V tervals betweenfenergy. impulses so that thecab signal control energy 'supplied to the section rails is of standard pattern and will operate existing cab signal apparatus. vIn addition, it will be seen that, when the section is" occupied, the equipment at the entrance end'of the section'operates to supply impulses'of feed-'back energyto the section rails to reset the track circuit when the section is Vacated v "`l Y In the'modication shown in Fig. v2, a code transmitter ZBCTfisfprov-ided to cause feed-back energy ltojebe supplied to therails of-an occupied section. This .supply of feed-'backenergyto the rails of an occupied section' can Abeeiected by interaction of the relays atl theentrance end of the section, thereby eliminating'vthfe need for the v a diagram illus-4 tratingsuch a modification. l l Construction `and operation;l of modification f islftowni;z'nQFig.I 3

Ink the modication shown 'in Fig; 3, the wire leading to relays IR and IRP isconnected over front contact 42 of relay H to an Ioutput terminal of the rectifier'associated with transformer IT, and is connected'over' `back contact 112v of relay H to contact 43of'relay'PC, Iwhilecontact 38 of relay H when pickedup connects the winding of relay PC to track relay contact 22 and, when released, to'back contact45 of-relay IRP. "Contact 46 of relay H controlsthe circuit of a winding of relay PC to render the relay slow acting when relay H is releasedl i" I The equipment is shown fin the condition which it assumes when the track' section is Vacant. At this tima-'energy is supplied through the decoding transformer DT to .relay H so its contacts are picked up with theyresult that energy is supplied from the "impulse transformer'IT to relays IR and IRP and relay PC is controlled by track relay contact 22 so thatimpulses of feed-back energy of alternately opposite polarity are supplied to the track rails'in'the lsame manner as explained in connection with Fig.`1. When the section 'is occupied, the track relay is shuntedf'anzlr energy lis no longer supplied through the transformer DT to relay H so relay H releases and transfers control of relay PC to a back contact of relay IRP andtransfers control of relays IR and'IRP to 'a front contactof relay PC.v 'On4 release of relays IR and IRP, energy is supplied over back contact 45 of relay IRP and hack contact38 of relay H torelay P C and its contacts pick up so that contact 43 establishes the circuit of relays YIR and IRP. Accordingly, relays IR and IRP pick up and establish the circuit for supplying energy from the battery'FB to the section rails, while contact 45 of relay IRP interrupts the circuit of relay PC. At this time, however, the lower winding of relay PC is short-circuited over back contact 46 of relay H so the relay is rendered slow to release and to pick up, and on picking up of relay IRP and resultant interruption ofthe circuit of relay PC, its contacts remain picked up for a short period and its contact 43 maintains the circuit of relay IR, while its contact 32 maintains the circuit of the upper portion of the battery FB so that an impulse of feed-back energy of reverse polarity is supplied'to the section rails.

After expiration of the release time of relay PCy its contacts release so contact 32 interrupts the supply of energy from the upper portion of battery FB and establishes the circuit to supply energy from the lower portion of battery FB so feedback energy of normal polarity is supplied to the section rails. contact 43 interrupts the circuit of relay 1R and, after a short time interval, relay IR releases to interrupt the supply of energy from the battery FB to the sectionrails and to also interrupt the circuit of relay IRP. Accordingly, relay IRP releases and completes connection of the track relay TR across the section rails while Contact t of relay IRP establishes the circuit to supply energy to relayPC. Because of the slow acting characteristic of relay PC at this time, its contacts do not pick 'up `for a short period. This Iinsures that relays IR and IRP will remain released and maintain the circuit of the track relay for a substantial period so that, when the section is vacated, impulses of master code can feed to the track relay and operate it to pick up relay H and reset the track circuit apparatus.,

when relay PC picks up, its Contact is 'estatlishes the circuit to supply energy to relays IR and IRP s'o that they pick up and the cycle just described is repeated. I f

When the sectionis Vacatedth'e feed-back energy supplied to the section rails feeds to the feed-back detector relay -at the exit end of the section and operates it as explained in connection with F-ig. 2 yto reset the equipment Aat the exit end of the section and thus cut off the supply of alternating 'current cab signal control energy to the section rails and reestablish the `supply of impulses of master code of alternate relative polarity to the section rails. Theseimpulses of energy feed tothe track relay TR during the released periods of the relays IR and IRP and operate the track relay so that energy is supplied to relay H. When relay H picks up, kits Contact 42 transfers control of relays IR and IRP to the im- When relay PC releases, its

' an impulse of energy pulse transformer IT, while Contact 38 of relay I-I v transfers control of relay PC to track relay contact 22, and contact 4E of relay H interrupts the circuit of the lower winding of relay PC. The equipment now operates in the normal manner as explained in detail above.

The various parts of the system shown in Fig. 3 are selected and proportioned sothat the rate of operation of the relays. IR, IRP and PC, when the section is occupied, is substantially. different from that of the code transmitters which govern the supply of master code to the section rails. This insures that there will be frequently recurring periods during which impulses of feed-back energy vcan feed to the feed-back detector relay and during which-impulses of master code can feed to the track relay so that resetting of the track circuit when the section is vacated will be prompt and positive.

In the modifications previously described, a re` peater -relay IRP for relay IR is provided to delay connection of the track relay TR across the section rails until energy stored in the track circuit has been dissipated to thereby prevent operation of the track relay by this energy. The track relay rnay also be protected from operation by stored energy and against overlapping contacts on the relay IR by supplying energy from the battery FB to the section rails in series With the track relay winding, and Fig. 4 is a diagram showing such a modification.

Construction and operation of m'odz'ftcation shown in Fig. 4

Referring to Fig. 4, the equipment shown therein is similar to that employed at the entrance end of the section shown in Fig. 1, but diners therefrom in that acontactv 48 of the track relay TR controls the polarity of the energy supplied from the feed-back batteryy FB, thereby eliminating the need for the relay PC,.While a contact of relay IR controls the circuits of the battery FB and of the track relay TR,

When'the relay IR is released, its contact 41 interrupts the circuit of the battery FB and establishes the circuit to connect the winding of the track relay TR across the section rails so that master code may feed to 'the track relay.I On the supply of an impulse of master code of rcverse polarity to the track relay, its contacts move from their normal to their reverse positions, while is supplied through transformer IT to relay IR and its contact 41 picks up to interrupt the circuit connecting track relay TR directly across the section rails and to connect the winding of the track relay across the section rails in series with the right-hand portion of the battery FB so that energy is supplied from the battery to the section rails through the track relay winding. l

At this time 'the positive terminal of the righthand half of the lbattery FB is connected over front contact 41 of relay IR to the right-hand terminal of the winding of the track relay and through this winding to the track rail I, while the negative terminal of this portion of the battery is connected over reverse polar contact 48 of relay TR to rail 2. Accordingly, at this time an impulse of feed-back energy of normal polarity is supplied to the Section rails, while the direction of flow of energy through the winding ofrelay TR is such that the contacts of relay TR are held in their reverse positions.

On release of the contact 41 of relay IR, the

l circuit of the battery AFB is interrupted and the winding of relay 'I'R is connected directly across the section rails. On interruption of the supply of energy from the battery FB to the section rails, energy stored in the track circuit continues to flow in the same direction that it has been flowing, and energy supplied from the track circuit to the winding of the track relay TR operates to hold the relay contacts in the position which they then occupy, that is, their reverse positions.

The next impulse of master code supplied to the section rails will be of normal polarity, and this energy will feed over back contact 41 of relay IR to the winding of relay TR and will move the contacts of relay TR to their left-hand or normal positions. On this movement of the track relay contacts, an impulse of energy is supplied through the transformers DT and IT to the relay IR and its contact 41 picks up to connect the left-hand portion of battery FB across the section rails in series with the winding of the track relay TR. 'I'he positive terminal of this portion of the battery FB is connected over normal polar contact 48 of relay TR to track rail 2, while the negative terminal of this portion of the battery is connected over front contact 41 of relay IR to the left-hand terminal of the Winding of relay TR, and through this Winding to track rail I. Accordingly, an impulse of feed-back code of reverse polarity is supplied to the section rails, While energy ows through the Winding of relay 'I'R from its left-hand to its right-hand terminal so the energy owing through the relay Winding holds the relay contacts in the positions which they then occupy, that is, their normal positions.

On release of the relay IR, the circuit of the battery FB is interrupted and relay 'IRis connected directly across the section rails. When the circuit of the battery FB is interrupted', energy stored in the track circuitV continues to flow in the direction in which it has been owing so this energy operates to hold the contacts of relay TR in the position which they then occupy, that is, their normal positions.

On continued supply of master code to the track relay, the contacts of this relay move from one position to the other, While after each movement of the track relay contacts, the impulse relay IR picks up to cause an impulse of feedback energy to be supplied to the track rails over a circuit which includes the winding of the track relay in series therewith, and the direction of ow of feed-back energy through the track relay Winding is such as to hold the track relay contacts in the position which they then occupy. In addition, the direction of oW of energy through the track relay Winding is such that when relay IR releases and interrupts the circuit of the battery FB, energy stored in the track circuit Will ilow through thevtrack relay Winding in the direction to maintain the relay contacts in the position which they already occupy so that there is kno possibility that the track relay will be operated by energy `stored in the track circuit.

The principle shown in Fig. 4 for preventing operation of the track relay by energy stored in the track circuit may also be employed to protect the feed-back detector relay, and Fig. 5 is-a diagram illustrating such a modification.

Construction and operation of modification shown in Fig. 5

In the modification shown in Fig. 5, the polarity of the energy supplied from the track battery TB to the section rails is controlled by contact 50 of the feed-back detector relay K, while the supply of energy to the transformer MT is controlled by contacts of the coding devices instead of by a relay which repeats these devices.

When relay HA is picked up, its contact I establishes the circuit controlled by the contact of coding device I80CT for supplying energy to the primary winding of transformer MT, so that each time the contact of coding device I 8CT picks up or releases, an impulse of energy is supplied through the transformer MT to relay MR.

When contact I of relay MR picks up at a time when the contact 5U of relay K is in its normal position, as shown, energy is supplied from the left-hand portion of the track battery to the section rails over the circuit which is traced from the positive terminal of this portion of the battery over front contact I5 of relay MR to rail 2, thence through the track relay, not shown, to rail I, through winding of relay K from left. to right,

and over normal polar contact 50 of relay Kto the negative terminal of the battery. The energy owing through the winding of relay K holds the relay contacts in their normal positions. When relay MR releases, its contact I5 interrupts the circuit of the battery TB and connects relay K across the section rails, while energy stored in the track circuit will flow through the winding of relay K in the direction to maintain its contacts in their normal positions.

When relay MR picks up at a time when the contacts of relay K are in their reverse positions, energy is supplied from the right-hand portion of battery TB to the section rails over the circuit which is traced fromthe positive terminal of this portion of the battery over reverse polar contact 50, through the winding of relay K from right to left to rail I, thence through the track relay winding, not shown, to rail 2, and over front contact l5 of relay MR to the negative terminal of this portion of the track battery. The energy supplied through the winding of relay K holds the relay` contacts in their reverse positions, while on release of relay MR the supply of energy from the track battery to the section rails is cut off and the relay K is connected across the'track rails, and energy stored in the track circuit will flow through the winding of relay K in the direction to hold the relay contacts in their reverse positions.

If, for any reason, the movable contact I5 of relay MR should engage its front and back contacts at the same time, the track battery Will be short-circuited and energy will not be supplied from the track battery to relay K which Amight cause operation of relay K.

In some situations it is necessary to divide a track section into two` subsections, and tor provide means for repeating into the rearward one of the sections the master code supplied'to vthe forward one of these sections and to 'also provide means governed by occupancy of the rear- Ward one of these sections for controlling the supply of feed-back energy tothe forward one of these sections, and Fig. 6 is a diagram illustrating code repeating equipment which may be employed at a cut-section installed for the control of a highway crossing signal.

Cut-section facilities of Fig. 6

The equipment of Fig. 6 is similar to that shown in Figs. 4 and 5 and employs the series supply of energy from the feed-back and track batteries shown in Figs. 4 and 5. It is Lcontemplated that the equipment at the entrance end of the track section Will be arranged as shown in either Fig. 2 or Fig.- 3y so that feed-back energy is supplied to the section rails when the section is occupied. The equipment at the exit end of the track section is arranged as shown in Fig. 1.

When the track section is vacant, master code supplied at the exit end of the section feeds to the track relay TR of the forward subsection and operates it so that energy is supplied through the decoding transformer DT and transformer MT to relay MR so that relay MR picks up to supply energy from battery TB to the section rails, while at this time relay K is operated by feed-back energy so that its contact 5i) causes alternate impulses of master code to be of op'- posite relative polarity. At this time, relay KH is picked up and its contact 52 establishes the circuit for supplying energy from the transformer IT to relay IR so that it picks up to supply energy from battery FB to the section rails. Accordingly, each time the contacts of relay TR move from one position to the other, relay IR picks up to supply an impulse of feed-back energy to the forward subsection, and relay MR picks up to supply an impulse of master code to the rearward subsection. The relay MR, therefore, repeats the relay TR so energy of the same code frequency is supplied to the rearward subsection and is supplied to the forward subsection.

As the relay KH is picked up, its contact d interrupts the circuit of the crossing signals XS to prevent operation of these signals at this time.

When a train travelling in the normal direction of traflic enters the rearward subsection, it cuts off the supply of feed-back energy over the section rails so that relay K ceases to operate. r'his causes relay KH to release so that Contact 54 establishes the circuit of the crossing signals XS and they operate to warn users of the highway of the approach of the train.

In addition, on release of relay KH, contact EZinterrupts the circuit of relay IR so that it remains released and does not supply feed-back energy to the forward subsection. Accordingly, the equipment at the exit end of the section operates to provide an indication at that point that the section is occupied.

At this time, the equipment at the entrance end ofthe reaward subsection operates as explained in connection with Fig. 2 or 3 to cause impulses of feed-back energy to be supplied to the section rails.

When the train advances into the forward subsection, the track relay vTR is shunted and ceases to follow code so energy is no longer supplied through transformers DT and MT to relay MR and itscontact remains released so that energy is no longer supplied from battery TB to the rails of the rearward subsection, while relay K is connected across the section rails.

When the train vacates the rearward subsection, impulses of feed-back energy supplied at the entrance end of this subsection feed to relay K and operate it so that energy is supplied through the decoding transformer KT to relay KH. Accordingly,v relay KH picks up and its contact 54 interrupts the circuit of the crossing signals XS and they cease operating, while contact 52 of relay KH establishes the circuit of relay IR. However, at this time, relay TR is shunted so energy is not supplied to relay IR and its contact remains released.

When the train vacates the forward subsection, impulses of master code supplied at the exit end of this subsection feed to the track relay TR and operate it so that energy is supplied through the transformer DT to the relays IR and MR and the relay IR operates to supply feed-back energy to the forward subsection, while the relay MR operates to supply impulses of master code to the rearward subsection. At this time, relay K is being operated by feed-back energy supplied at the entrance end of the rearward subsection so the contacts of relay K are constantly being moved between their two positions. Accordingly, on repeated picking up of the contact I5 of relay MR to establish the circuit of the track battery TB, there are frequent reversals in the polarity of the energy supplied to the section rails. As explained abovein connection with Figs. 2 and 3, the frequency of the feed-back energy is substantially different from that of the master code supplied to the section rails so there are frequently recurring periods in which master code supplied to the track rails may feed to the track relay and operate it to reset the apparatus at the entrance end-of the section so that thereafter the supply of feed-back energy to the section rails is governed by operation of the track relay.

From the foregoing, it Will be seen that the equipment shown in this modification operates to initiate operation of the highway crossing signals when a train enters the track section and to discontinue operation of the crossing signals whenthe train vacates the rearward subsection, while the equipment also operates to provide an indication of occupancy of the track section at the exit end of the section as long as either subsection is occupied.

In the modification described above, the relays IR and IRP which control the supply of feedback energy to the section rails have been energized through an impulse transformer which is proportioned to limit the value of the energy impulse supplied to the relay IR so that the contacts of relay IR will remain picked up for a predetermined period. It is possibleto control the supply of energy to relays IR and IRP by contacts of the relays TR and PC and thus eliminate the transformer IT, and Fig. '7 is a diagram showing such a modification.

Construction and operation of modification Shown in Fig. 7

The apparatus shown in Fig. 7 is similar to that employed at the entrance end of the section shown in Fig. l, but differs therefrom in that the supply of energy to relays IR and IRP is controlled by contact 55 of relay TR and by contact 58 of relay PC.

When the contacts of relay TR are in their normal positions, as shown, contact 22 of relay TR interrupts the circuit of relay PC so'the contacts of relay PC are released and contact 55 interrupts the circuit of relays IR and IRP.

On movement of the track relay contacts to their reverse positions, contact 22 establishes the circuit for supplying energy to relay PC, while contact 55 of relay TR establishes the circuit including back contact 5S of relay PC for supplying energy to relays IR and IRP. The supply of energy to relays IR and IRP is cut off as soon as relay PC picks up, but relay PC remains released long enough subsequent to movement of the track relay contacts to their reverse positions to permit suflicient energy to be supplied to relays IR and IRP to causeA their contacts to pick up and to cause the contacts of relay IR to remain Picked up for a predetermined period.

Similarly, on movement of the track relay contacts from their reverse to their normal positions, energy is supplied to relays IR and IRP over the circuit which includes front contact 5B of relay PC and normal polar contact 55 of relay TR. At this time, track relay contact 22 interrupts the circuit of relay PC so its contacts release and contact 56 cuts oiI the supply of energy to relay IR. However, the contacts of relay PC remain picked up long enough subsequent to movement of the contacts of relay TR to their normal positions to permit sufficient energy to be supplied to relays IR and IRP to cause their contacts to pick up and to cause the contacts of relay IR to remain picked up for a predetermined period.

When the section is occupied, the contacts of the track relay remain in one position or the other, while the contacts of relay PC remain picked up or released, depending on-the position of the track relay contacts, and the circuit of relays IR and IRP will be interrupted so that these relays are released and establish the cir-v cuit of the track relay. Accordingly, master code will be supplied to the track relay as soon as the section is vacated.

The principle employed in Fig. 7 for the ccntrol of the relays IR and IRP may also be employed 'to control the relays MR and MRP and Fig. 8 is a diagram illustrating such a modication.

M odificaltion shown in Fig. 8

The equipment shown in Fig. 8 is similar to that employed at the exit end of the track section shown in Fig. 1 except that the supply of energy to the relaysl/IR and MRP is controlled by a contactl of the relay CTM and by contacts of the coding devices ISUCT and 15CT instead of being supplied through a transformer MT.

When relay HA is picked up, its contact I G establishes the circuit controlled by coding device ISUCT for supplying energy to coding relay CTM and to relays MR and MRP over back contact Il of relay CTM. In addition, contact ID of relay HA establishes a circuitI controlled by a contact of coding device |80CT for supplying energy to relays MR and MRP over front contact l I of relay CTM.

When the contact of coding device |8IJCT is picked up, as shown, energy is supplied over front Contact l of relay HA to relay CTM so that the contacts of relay CTM are picked up and contact Il interrupts the circuit of relays MR and MRP. On release of the contact of coding device IBBCT,

the supply of energy to relay CTM is cut off,

while energy is supplied over front' contact l0 of relay HA and front contact I! of relay CTM to relays MR and MRP. The supply of energy to relays MR and MRP is cut off as soon as contact l l of relay CTM releases, but the contacts of relay CTM remain picked up long enough subsequent to release of the coding device contact to permit sufficient energy to be supplied to relays MR and MRP to pick up their contacts and to maintain the` contacts of relay MR picked up for a predetermined period, after which the relays MR and MRP release and connect relay K across the section rails.

Similarly, when the contacts of coding device IBQCT pick up, energy is supplied to relay CTM, and is also supplied over back contact l I of relay CTM to relays MR and MRP. The supply of energy to relays MR and MRP is cut oi as soon as contact ll of relay CTM picks up, but sufiicient energy is supplied to relays MR and MRP prior to picking up of-the contacts of relay CTM to pick up the contacts of -relays MR and MRP and to keep the contacts of relay MR picked un for a predetermined period. l

An asymmetric unit 62 is included in series with thev circuit for supplying energy-to relays'MR and MRP to prevent 4interference with the re lease time of these relays by the relay CTM.

It will be seen that the apparatus of 8 operates to supply energy to relaysMR and MRP when the contacts of relay CTM and of coding device IBDCT are-out of correspondence. relays MR and MRP, therefore, pick up each time the coding device contacts pick up or release.

When relay HA is released, the supply of energy to relay CTM and to relays MR and MRP is controlled by a contact of coding device TC'I,

The

While the equipment operates in the manner explained in detail above.

The principle employed in the modication shown in Figs. 7 and 8 is also applicable to track sections in which cab signal energy is supplied to the rails of the section when the section is occupied, and Fig. 9 is a diagram showing this application of the invention.

Modification shown in Fig. 9

In Fig. 9 only the equipment atthe exit end of the section is shown, and the equipment at the entrance end of the section may be arranged `as shown in Fig. 2 or 3. The equipment of Fig. 9 is shown in the condition which it assumes when the track section is vacant. At this time, relay K is operated by feed-back energy and relay KH is picked up so that its contact 35 short-circuits the primary Winding of track transformer TT, While contact 64 of relay KI-I establishes the circuit controlled by code transmitters ISUCT and 'l5CT for supplying energy to coding relay CTM, and the equipment operates in the same manner as that shown in Fig. 8.

When a train enters the track section and cuts off the supply of feed-back energy to relay K, the relay KH releases and its contact 35 establishes the circuit for supplying energy to track transformer TT, while contact B4 of relay KH inter'- rupts the circuit of relay CTM so that the contacts of relay CTM remain released. On continued operation of the code transmitter NWOT, energy is supplied over `back contact il of coding relay CTM to relays MR and MRP vduring the picked-up periods of the contact of code'transmitter IBUCT so the relays MR and MRP operate as repeaters of the code transmitter. During the picked-up periods of the relays MR and MRP, energy is supplied from the track transformer TT to the section rails, and as the relays MR Y"and MRP operate as repeaters of the code transmitter Vat this time, the impulses of alternating current supplied to the section rails are of standard patternand ywill operate cab signal equipment of standard construction.

When the section is vacated, feed-back energy supplied at the entrance end of the section feeds to' relay K during the released periods of the relays MR and MRP and operates relay K to pick up relay KH and cut 01T the supply of energy to track transformer TT and establish the circuit of coding relay CTM sorthat the equipment operates'to supply impulses of master code of alternately opposite polarity to the section rails.-

The principle employed in the modifications shown in Figs. 7, 8 and 9 is also applicable to the track relay end of a track section in Which feedback energy is supplied to the section rails when the section is occupiedfand Fig. l0 is a diagram showing this application of the invention.

Modijcation shown in Fig. 10

The apparatus of Fig. 10 is similar to that of Figs. 3 and 7 and is shown in the condition which it assumes When the track section is vacant. At this time, the track relay TR is operated by mas- --ter code energy supplied over the section rails When a train enters the section, the `track relay ceases to operate and relay H releases so that contact 38 transfers control of relay PC to back contact 45 of relay IRP and contact 42 transfers control of relays IR and IRP to front contact 43 of relay PC. The equipment now operates in substantially the same manner as that shown in Fig. 3. On release -of relay IRP, energy is supplied to relay PC and its contacts pick up to cause energy to be supplied to relays IR and IRP so that they establish the circuit including front contact 32 of relay PC for supplying energy from battery FB to the section rails, while contact 45 of relay IRP interrupts the circuit of relay PC. Accordingly, relay PC kreleases so that ener-gy is supplied from battery FB to the section rails over back contact 32, while contact 43 interrupts the circuit of relays `IR and IRP and they release so the cycle is repeated. At this time, the l-ower winding of relay PC is short-circuited over contact 46 of relay H so relay PC is slow to pick up and release and its contacts remain released long enough during each cycle to permit master code supplied to the section rails to operate the track relay and reset the apparatus when the section is vacated.

In some situations, it is desirable to employ the feed-back energy for a track section t0 indicate occupancy of the section in the rear of that section as well as of the section over which the feedback energy is supplied. This result may be accomplished by controlling the polarity relationship of the feed-back impulses with respect to the master code impulses, and Fig. 1l is a diagram illustrating such a modification.

Modification shown in Fig. 11

The apparatus shown in Fig. 11 is similar to that shown in Fig. 1 but differs therefrom in that the equipment at the entrance end of the track section includes a relay KHB which is governed .by traflic conditions in the adjacent section in `the rear and controls connection of relay PC to a normal or a reverse polar Contact -of the track relay. The equipment at the exit end of the section includes a polar relay KP and a biased polar relay KN, which are energized in series from the secondary winding of the decoding transformer KT, while the polarity of the energy supplied to these relays is determined by contact 65 of relay CTM. The yrelays KP and KN are energized through asymmetric units in the manner shown in Letters Patent of the United States No. 2,324,- 200, granted July 13, 1943 to Arthur E. Dodd.

The equipment is shown in. the condition which it assumes when the track stretch is vacant. At this time, relay HA is picked up so relay CTM is operated by energy of 180 code frequency, while contact 6B of relay KHB is picked up and Connects relay PC to reverse polar .Contact 22 of relay TR.

Each time the contacts of relay CTM pick up, an impulse of energy is supplied through transformer MT to relays MR and MRP `and they pick up so that energy is supplied from the upper portion of track battery TB to the section rails. The positive terminal of this battery is connected to track rail I so the master code supplied to the section rails may be considered to be of normal polarity.

Each time the contacts of relay CTM release, an impulse of energy is supplied to the section rails from the lower portion of the track battery. At these times, the positive terminal of the track battery i-s connected to rail 2 so the master code may be considered to Abe of vreverse polarity.

The impulses of master code of normal polarity feed to the track lrelay TR and move its contacts to their left-hand or normal positions, with the result that an impulse of energy is supplied to relays IR and IRP so `that they pick up to supply an impulse of feed-back energy to the section rails, while relay PC releases so that the impulse of feed-back energy is supplied from the lower -portion of the battery FB. The positive terminal of this portion of the battery is connected to track rail I so the impulse of feed-back energy supplied to the section rails may be considered to be of norma polarity.

Similarly, when an impulse of master code of reverse polarity feeds to the trackrelay, an impulse of lfeed-back energy is supplied to the section rails from the upper portion of battery FB. The positive terminal of this portion of the battery is connected to track rail 2 so that the impulse of feed-back energy supplied at this time is of reverse polarity.

Accordingly, when relay KHB is -picked up, each impulse of master code of normal Ipolarity is followed by'an impulse of feed-back code of normal polarity, and each impulse of master code of reverse polarity is followed by an impulse of .feed-back code-of reverse polarity.

The impulses .of feed-back energy supplied to the relay K move its contact 6T to its normal orA reverse position depending upon the polarity of the impulse. On movement of the contact 61 to its `normal position, energy flows through the left-hand portion of the primary winding of transformer KT from left to right, and causes an impulse of energy to be induced in the transformer secondary Winding. For purposes of illustration, it will be assumed that the transformer windings are arranged so that the impulse of energy induced .in the secondary winding at this time flows from left to right in this winding.

If the impulse of feed-back energy of normal polarity follows an impulse of master code of normal polarity, the movement of the contact of relay K to its normal position occurs at a time when the contacts of relay CTM are picked up.

Accordingly, energy induced in the left-,hand portion of vthe transformer secondary Winding flows from the center terminal of the transformer secondary winding through the Windingl of relay KP from left to right, normal polar con tact 'l0 of relay KP, through winding of relay KN from left to right, asymmetric unit 1l, and front contact 65 of relay CTM to the left-hand end terminal of the secondary winding of transformer KT. The impulse of energy supplied to relays KP and KN holds the contacts of relay KP in their normal positions, and energizes the relay KN so that its contacts remain picked up. The transformer KT is so proportioned that the impulse of energy supplied therefrom is of relatively short duration so the impulse is substantially terminated before the contacts of relay CTM release to supply the next impulse of master code to the section rails.

Similarly, when an impulse of feed-back energy of reverse polarity is supplied to relay K and its contact 61 moves to its reverse position, the right-hand portion of the primary winding of transformer KT is energized, and an impulse of energy is induced in the transformer secondary winding which flows from right to left in that winding. If the impulse of feed-back energy of reverse polarity follows an impulse of master code of reverse polarity, the movement of the' contact of relay K to its reverse position will occur at a time when'the contacts of relay CTM are released.

Accordingly, energy induced in the right-hand portion of the secondary winding of transformer KT ows from the center terminal of the transvformer secondary winding through the winding of relay KP from left to right, normal polar contact 10, winding of relay KN from left to right, asymmetric unit 1I, and back contact 65 of relay C'IM to the right-hand end terminal of the transformer secondary winding.

The energy supplied to relays KP and KN at this time holds the contacts of relay KP in their normal positions, and maintains the contact of relay KN picked up, while the impulse of energy from the transformer secondary winding terminates before the contacts of relay CTM pick up to supply the next impulse of master code to the section rails.

Accordingly, on continued supply of feed-back energy to relay K, energy is supplied from transformer KT to relays KP and KN, While the contact 65 of relay CTM recties the energy supplied from transformer KT to relays KP and KN so that the energy impulses are all of normal polarity.

As explained in the patent of Arthur E. Dodd identified above, the asymmetric units connected across the terminals of relay KN render the relay slow in releasing so its contacts remain picked up during the periods between the impulses of energy supplied to the relay KN.

The contact 'I2 of relay KN and normal polar contact 14 of relay KP may cooperate to control a circuit which may be employed for any appropriate purpose as, for example, to unlock a switch.

When the section in the rear of the section shown is occupied, relay KHB is released and its contact 66 transfers control of relay PC from reverse polar contact 22 of relay TR. to normal polar contact 22 of relay TR. Thereafter. on the supply of an impulse of master code of normal polarity to the track relay TR, relay PC picks up so the impulse of feed-back energy supplied to the section rails is of reverse polarity. Likewise, when an impulse of master code of reverse polarity is supplied to the track relay, the relay PC releases so the impulse of feed-back energy supplied to the section rails is of normal polarity.

When the impulse of feed-back energy of reverse polarity feeds to relay K following an impulse of master code of normal polarity, the contact of relay K will move to its reverse position at a time when the contacts of relay CTM are picked up, and energy from the left-hand portion of the secondary winding of transformer KT will ow from the left-hand end terminal of this Winding over front contact 65 of relay CTM, through asymmetric unit 15, normal polar contact 1U of relay KP, and through the winding of relay IQ from right to left to the center terminal of the transformer secondary winding. This energy causes the contacts of relay KP to shift to their reverse position so that thereafter energy from the left-hand portion of the transformer secondary winding flows overfront contact 65 of relay CTM through. asymmetric unit l5, winding of relay KN from left to right, reverse polar contact 'i6 of relay KP, and through winding of relay KP from right to left to the center terminal of the transformer secondary Winding.

Similarly, when the impulse of feed-back energy of normal polarity feedsto relay K following an impulse of master code of reverse polarity, the contact 61 of relay K moves to its normal position at a time when the contacts of relay CTM are released, and energy from the right-hand portion of the secondary winding of transformer KT flows from the right-hand end terminal of the transformer secondary winding over back contact 65 of relay CTM, asymmetric unit 15, through winding of relay KN from left to right, reverse polar contact l0 of relay KP, and through Winding of relay KP from right to left to the center terminal of the transformer secondary winding.

Accordingly, when relay KHB is released so that each impulse of master code is followed by an impulse of feed-back energy of opposite polarity, the energy supplied from transformer KT to relays KP and KN is of reverse polarity and the contacts of relay KP occupy their reverse positions, while the contact of relay KN is picked up. When the contacts of relay KP are in their reverse positions, contact 14 interrupts the circuit established in the normal position of the contact, and may establish another circuit which may be employed for any appropriate purpose.

From the foregoing it will be seen that when feed-back energy is supplied to the relay K, an impulse of energy is supplied through the transformer KT to the relays KP and KN on each movement of the contact of relay K, while the energy supplied from the transformer KT is rectified by contact 65 of relay CTM. The operation ofy contact 65 is such that if-the polarity of the feed-back impulses is the same as that of the preceding impulses of master code, the energy supplied from transformer KT to relays KP and KN will be of normal polarity, while if the polarity of the feed-back impulses is opposite `from that of the preceding impulses of master code, the energy supplied from the transformer KT to the relays KP and KN will be of reverse Polarity. The relays KP and KN distinguish -between the two polarities of energy supplied from the transformer and thus provide means for detecting which of the two types of feed-back energy is beingv supplied over the section rails.

When a train enters the section, the track relay TR ceases to follow code and the supply of feedback energy is cut olf and relay K ceases to fol-y TR and operates it sothat feed-back energy is again supplied to the section rails so that relay K operates to cause energy to be Supplied through vtransformer KT to relays KP and KN.

Although I have herein shown and described ,severall forms of codedtrack circuit apparatus embodying my invention, it is Yunderstood that various changes and modifications may be made '4 therein within the scope of the yappended claims without departing from the' spirit and scope of my invention.

vHaving thus claim is: I

1. In combination, a section of railway track, a first and a second coding relay and a polarized described my invention, what I detector relay at the exit end of the section, the

rst coding relay having contactscontinuou-sly actuated between a first and a. second position.

detector relay between the second coding relay having contacts biased '.to .a released .position in which they connect the detector relay across the 4section rails and being movable to a picked-up position in which they cause to be supplied to the section rails energy of normal or reverse polarity according as the contacts of the first coding relay are in their first or their second position, means effective on movement of the contacts of said first coding relay between their two positions in either direction to Vpick up the contacts of the second coding relay for a predetermined period substantially shorter than the periods that the contacts of the rst coding relay remain in each of their two positions, a control relay responsive to movement of a contact of the its two positions, a polarized coole following track relay at the entrance end of the track section operated by energy 'supplied over the section rails, and means effective on movement of the track relay contacts to their normal position to supply to the section rails an impulse of energy of one polarity and effective on movement of the track relay contacts to their reverse position to supply to the section rails an impulse of energy of the other polarity.

2. In combination, a section of railway track, a first and a second coding relay and a polarized detector relay at the exit end of the section, the first coding relay having contacts continuously actuated between a first and a second position, the second coding relay having contacts biased to a released position in which they connect the detector relay across the section rails and being 'movable to a picked-up position in which they cause to be supplied to the section rails energy of normal or reverse polarity according as the `contacts of the first coding relay are in their rst or their second position, means effective on movement of the contacts of said first coding relay between their two positions in either direction to pick up the contacts of the second coding relay for a predetermined period substantially shorter than the periods that the contacts of the first coding relay remain in each of their two positions, a control relay responsive to movement of a contact of the detector relay between its two positions, a polarized code following track relay at the entrance end of the track section operated by energy supplied over the section rails,

an auxiliary relay responsive to movement of a contact of said track relay between its two positions. means effective when said auxiliary relay is picked up to supply to the section rails an impulse of energy of one polarity on movement of the track relay contacts to their normal yposition and to supply to the section rails an impulse of energy of the other polarity on movement of the track relay contacts to their reverse position, and means effective when said auxiliary relay is released to alternately connect said track relay and a supply circuit across the section rails and to cause alternate impulses of energy supplied over said supply circuit to the section rails to be of opposite polarities.

3. In combination, a section of railway track, a polarized code following detector relay at the exit end of said section, a control relay responsive to movement of a contact of the detector relay between its two positions, code transmitting means for alternately connecting said detector relay and a supply circuit across the section rails and for causing the impulses of energy supplied over said Supply circuit to the section rails to be of alter- `nately opposite polarities, a polarized code fol- .flowing track relay kat the entrance end of said section operated by `energy supplied over the 'section rails, an auxiliary relay responsive to movement of a contact of said track relay between its two positions, means effective when said auxiliary relay is picked up to supply to the .section rails an impulse of energy of one polarity on movement of the track relay contacts to their normal position and to supply to the section rails an impulse of energy of the other polarity on movement of the track relay contacts to their reverse position, and lmeans effective when said auxiliary relay is released to alternately connect said track relay and a supply circuit across the section rails and to cause alternate impulses of energy supplied over said supply circuit to the section rails to be of opposite polarit-ies.

4. In combination, a section of railway track,

`'a polarized code following detector relay at the exit end of said section, a control relay responsive to movement of a contact of said -detector relay between its two positions, a first coding relay having contacts continuously actuated between a first and Ia second position, a second coding relay having contacts biased to a released position in which they connect the track rails across the detector relay winding and being movable to a picked-up position in which they connect the track rails across a pair of supply conductors over which is supplied direct current of one polarity or the other according as the contacts of the first coding relay are in their first or their second position and over which alternating current is supplied when the control relay is released, means effective on movement of the contacts of the first coding relay between their two positions in either Ydirection when the control relay is picked up to pick up the contacts of said second coding relay for a predetermined period substantially shorter than the periods that the `contacts of the first coding relay remain in each of their two positions, means effective when the control relay is released to pick up the contacts of the second control relay as long as the contacts of the first control relay are in a selected one of their two positions, a polarized code following track relay at the entrance end of the section operated by energy supplied over the section rails, an auxiliary relay responsive to movenient of a contact of said track relay between its two positions, means effective when said auxiliary relay is picked up to supply to the section rails an impulse of energy of one polarity on movement of the track relay contacts to their normal position vand to supply to the section rails an impulse of energy of the other polarity on `movement of the track relay contacts to their reverse position, and means effective when said auxiliary relay 'is released to alternately connect said track relay and a supply circuit across ,the section rails and to cause alternate impulses of energy supplied over said supply circuit to the section rails to be of opposite polarities.

5. In combination, a section of railway track, a polarized code following detector relay at the exit end of lsaid section', a control relay responsive to movement of a contact of the detector relay between its two positions, code transmitting means for alternately connecting said detector relay and a supply circuit across the section rails and for causing the impulses of energy supplied over said supply circuit to the section rails to be of alternately opposite polarities, a polarized code following track relay at the entrance end of said section operated by energy supplied over the section rails, an auxiliary relay responsive to movement `of a contact of said `track relay between its two positions, an impulse relay having contacts biased to a released position in which they connect the section rails across the terminals of the winding of said track relay and movable therefrom to a picked-up position in which they connect the section rails across a pair of supply conductors over which energy is supplied to the section rails, a pole changing relay having contacts biased to a released position in which they cause the energy supplied over said supply con-y ductors to be of one polarity and movable therefrom to a pick-up position in which they cause the energy supplied over said supply conductors to be of the other polarity, means effective on movement of the track relay contacts between their two positions in either direction when the auxiliary relay is picked up to momentarily pick up the contacts of said impulse relay, means effective on movement of the track relay contacts to a selected one of their positions when the auxiliary relay is picked up to pick up the contacts of said pole changing relay, and means eiectivewhen the auxiliary relay is released to continuously actuate the contacts of said impulse relay between their released and picked-up positions and to control the pole changing relay in such manner that the impulses of energy supplied to the section rails as a result of picking up of said impulse relay are of alternately opposite polarities.

6'. In combination, a section of railway track, a polarized code following detector relay at the exit end or" said section, a control relay responsive to movement of a contact of the detector relay between its two positions, code transmitting means for alternately connecting said detector relay and a supply circuit across the section rails and for causing the impulses of energy supplied over said supply circuit to the section rails to be of alternately opposite polarities, 'a polarized code following track relay at the entrance end oi' said section operated by energy supplied over the section rails, an auxiliary relay responsive to movement of a contact of said track relay between its two positions, an impulse relay having contacts biased to a released position in which they connect the section rails across the terminals of the winding of said track relay and movable therefrom to a pick-up position in which they connect the section rails across' a pair of supply conductors over which energy is supplied to the section rails, a pole changing relay having contacts biased to a released position in which they cause the energy supplied over said supply conv ductors to be of one polarity and movable therefrom to a picked-up position in which they cause the energy supplied over said supply conductors to be of the other polarity, a circuit including a front contact of said auxiliary relay for supplying to the impulse relay an impulse of energy on movement of the track relay contacts between their two positions in either direction, a circuit including a front contact of said auxiliary relay ior supplying energy to said pole changing relay when the track relay contacts are in a selected one of their two positions, a circuit including a back contact of said auxiliary relay and a front contact of said pole changing relay for supplying energy 4to said impulse relay, and a circuit including back contacts of said impulse and auxiliary relays for supplyingA energy to said pole changing relay.

7. In combination, a section of railway track, 75

a polarized code following detector relay at the exit end of said section, a control relay responsive to movement of a contact of the detector relay between its two positions, code transmitting means for alternately connecting said detector relay and a supply circuit across'the section rails and for causing the impulses kof energy supplied over said supply circuit tothe section rails to be of alternately opposite polarities, a polarized code following track relay at the entrance end of said section operated by energy supplied over the section rails, an impulse relay having a contact biased to a released position in which it connects the section rails across the terminals of the winding of said track relay and movable to a picked-up position in which it connects the section rails across a pair of supply conductors in series with the winding of said track relay, a contact of said track relay controlling the polarity of the energy. supplied over said supply conductors in such manner that energy of one-polarity is supplied in one` position of the track relay contact and energy of the other polarity is supplied in the other position of the track relay contact and so that in each position of the track relay contact the energy supplied through the track relay winding holds the track relay contacts in the position which they then occupy, and means for supplying an impulse of energy to said impulse relay on movement of the track relay contacts between their two positions in either direction;

8. In combination, a section of railway track, a polarized code following detector relay at the exit end of said section, a coding relay having a contact movable between a iirst position in which it connects the section rails across the terminals of the winding of said detector relay and a second position in which it connects the section rails lacross a pair of supply conductors in series .with the winding of said detector relay, a contact of said detector relay controlling the polarity of the energy supplied over said supply conductors in such manner that energy of one polarity is supplied in one position of the detector relay contact and energy of the other polarity is supplied in the other position of the detector relay contact and so that in each position of the detector relay contact the energy supplied through the detector relay winding holds the relay contacts in the position which they then occupy, a polarized code following track relay at the entrance end of said section operated by energy supplied over the section rails, `an auxiliary relay responsive to movement of a contact of said track relay between its l two positions, means effective when said auxiliary relay is picked up to supply to the section rails an impulse of energy of 'one polarity on movement of the track relay contacts to their norma1 position wf and to supply to the section rails an impulse of p energy of the other polarity on movement of the track relay contacts to their reverse position, and means effective when said auxiliary relay is ren leased to alternately connect said track relay and a supply circuit across the section rails and to cause alternate impulses of energy supplied to the section rails to be of opposite polarities. e

9. In combination, a section of railway track, a iirst and a second coding relay and a polarized detector relay at the exit end of the section, the iirsty coding relay having contacts continuously actuated between a rst and a second position, the second coding relay having contacts biased to a released position in which they connect the detector relay across the section rails and being movable to a pickedup position in which vthey cause to be supplied -to the section rails energy of normal or reverse polarity according as'fthe contacts of the nrst coding relay are in their rst or their second position, meansI effective on movement of the contacts of said first 'coding relay between theirtwo positions in either direc'- tion to pick up the contacts of the 'second coding relay for a predetermined period 'substantially shorter than the periods that the contacts of the first coding relay remain in each of 'their 'two positions, a polarizedcode following track relay at the entrance end of vthe section operated by energy supplied'over thev section rails, means elective on movement oi the track relay contacts between their two positions in either direction to supply an impulse of energy to the section rails, means ffor controllingthe polarity of the energy impulses supplied 'to the section 'rails as a result of operation 'of the track relay in siic'h manner that at times energy of normal polarity is vslipplied to the section rails on movement of the track relay contacts to 'their normal position vand energy of reverse polarity is supplied to the section rails on Inoyenlent of the trackrel'ay contacts to their reversepostion and at other times energy of reyerse polarity is supplied to the secr tion rails on movement 'of the track relay "contacts to their normal position and energy of nor'- mal polarity 'is snpplied to the section rails on movement 'of the track relay contacts to their reverse position, polarized control n'e'ans at the exit end of said section, Vmeans responsive to movement cfa 'contact of said detector 'relay "between its two positions for supplying energy 'to said control means, and means governed by 'the relative positions of the contacts of Said detector relay and of said nist coding relay for determining the polarity of the energy 'supplied to Said control means. 'l y f 10. In combination, a section of railway track, a first and a secondcodi'ng relay and a polarized detector relay 'at the "enit end of the section, the rst coding relay having contacts continuously actuated between a rst Yand va second position, the second Ycoding relay having contacts biased to a released 'position in which Ythey connect the detector relay across the section rails vandbeing Vmovable vto a picked-np position in which't'hey cause to be supplied to the section rails energy of normal or 'reverse polari@ 'according as the Contacts ofthe first Coding relay are Ain their Lnrs/t or their second position, 'means effectivefon Inovement of -the contacts -'of said first codingr relay between their two 'positions in either direction rto their two positions 4in'eitlier direction i'to supply y at times energy'of normal polarityis supplied toy the sectionrailson movement of the trackrelay contacts to their norn'ial position and .energy of reverse polarity is 'supplied to the section rails "on movement of theltrackrelaycontacts'totheir reverse position and at other times*energyv of 'reverse polarity ris supplied to'the section rails on 7'5 movement vof the track relay contacts to their normal position andV energy of normal polarity is supplied to 'the section rails on movement of the track relay contacts to their reverse position, polarized control means at the exit end of said section, and means for supplying energy of one polarity to said control means if the detector relay contact moves to its normal position when the contacts of the first coding relay are in their first position and if the detector relay contact moves to its reverse position when the contacts of the rst coding relay are in their second position and for supplying energy of the other polarity to said control means if the detector relay contact moves to its normal position when the contacts of the rst coding relay'are in their second position and if the detector relay contact moves to its reverse position when the contacts of the rst coding relay are in their nrst position.

ll. In combination, a'section of railway track, a polarized code following detector relay at the exit end of said section, a coding relay having contacts continuously actuated between a iirst and a second position, means effective on movement of the contacts of said coding relay to their nrst position to supply to the section rails an impulseof energy of normal polarity and to thereafter connect the detector relay across the section rails, means eective on movement of the 'contacts of said coding relay to their second position to supply to the section rails an impulse of energy of reverse polarity and to thereafter connect thel detector relay across the section rails, polarized control means at the exit end of the section, means for supplying energy of one polary ity tosaid control means if the detector relay contact moves to its normal position when the contacts of said coding relay are in their rst position and lif the detector relay contact moves to its reverse position when the contacts of said coding relay are in their second position, means for supplying energy of the other polarity to said control means if the detector relay contact moves to its normal position when the contacts of said coding relay are in their second position and if 'the detector relay contact moves to its reverse position when the lcontacts of said coding relay are in their first position, a polarized code following track relay at the entrance end of the section operated by energy supplied over the section rails, means effective on movement of the track relay `contacts between their two positions in either direction to supply an impulse of energy to thesection rails, means for controlling the polarity of the energy impulses supplied to the section rails as a result of operation of the track relay' in such manner that at times energy of normal polarity is supplied to the section rails on movement of the track relay contacts to their normal position and energy of reverse polarity is supplied to the section rails on movement of the track relay contacts to their reverse position and at other times energy of reverse polarity is supplied to the section rails on movement of the track relay contacts to their normal position and l energy of ynormal polarity is supplied to the sec- 'exit end of said section, a coding relay having contacts continuously actuated between a first and a second position, means effective on move- `ment of the contacts of said coding relay to their first position to supply to the section rails 

